The Circle of Despair

The ancient fortress of the Witch King of Angmar is rumoured to be surrounded by eight dread towers within which his lieutenants resided during the long war with Arnor, weaving their dread magic there against the forces of the West.

Places:
Find Minas Caul (7.8N 23.0W)
Find Minas Agar (7.2N 23.2W)
Find Minas Maur (6.6N 22.9W)
Find Minas Angos (6.3N 22.4W)
Find Minas Nîr (7.8N 21.8W)
Find Minas Deloth (6.6N 21.8W)
Find Minas Gularan (7.1N 21.6W)
Find Minas Dhem (8.0N 22.4W)

Tips from Mazzlefizz http://forums.lotro.com/showthread.php?t=111294

Caur is the easiest to get to. If you follow the road from Gath Forthnir, you'll smack right into it.

Altitude-wise, they are all about halfway up the tower so you need to find a high altitude approach. Fortunately, each tower has straightforward path that leads right to the door. You just have to be at the correct high altitude spot first to be able to be able to access it.

I approached almost all of the locations by circling counter-clockwise. There is a weird, narrow mountain path you can follow that is at the right altitude and gives you access to the paths. Just stay on the outside and try to go higher, and you'll eventually find the path. It may seem far away, but this path will put you at the correct altitude to get to the different doors.

The one exception for me was Minas Dhem, the north one. I approached that by circling clockwise from the graveyard. That does take you through an area that is kinda tough with all the densely populated wights; nonetheless, it is a far shorter path, making it less likely something will go wrong. That said, if you prefer, you can use the counter-clockwise path. Both will get you there.